﻿using System;

class Program
{
    static void Main()
    {
        int n1;
        int n2;
        float fn1 = 1;
        float fn2 = 1;
        float fn3 = 1;
        float cn;
        int n = int.Parse(Console.ReadLine());
        if (n >= 0)
        {
            n1 = n * 2;
            do
            {
                fn1 *= n1;
                n1--;
            }
            while (n1 > 0);
            n2 = n + 1;
            do
            {
                fn2 *= n2;
                n2--;
            }
            while (n2 > 0);
            do
            {
                fn3 *= n;
                n--;
            }
            while (n > 0);
            cn = fn1 / (fn2 * fn3);
            Console.Write("Cn = ");
            Console.WriteLine(cn);
        }
        else
            Console.WriteLine("ERROR");
    }
}